Are you exercising enough to make you sick?

Should you go harder or go longer?

Marathon and endurance races are increasingly popular, as is a new thirst for intense exercise, such as in ‘spike’ or ‘buzz’ intensity training methods and classes. But which is better for you? Or, to put it another way, which will do least damage to your immune system?

New research by Bangor University challenges the current thinking that longer, less strenuous workouts are less harmful to the immune system.

The new findings (published in Medicine & Science in Sports & Exercise - Exercise intensity and duration effects on in vivo immunity November 2014 DOI: 10.1249/MSS.0000000000000562) show that half-an-hour of very intense exercise does not affect the immune response but that more long-lasting exercise at a moderate intensity decreases immunity.

Conducted for the first time using real people, as opposed to test tubes, cells or artificial ‘lab’ experiments, and measuring the exercising body’s actual immune response to a skin patch test applied after different durations and intensities of exercise, the research results clearly imply that long periods of moderate exercise will reduce your immune system’s capacity- making you more likely to succumb to any opportunistic bugs that might be around. Short duration intense workouts, however, were found to have no significant effect on the body’s immune system.

Prof Walsh and his team at Bangor University administered a chemical called diphenylcyclopropenone (DPCP) through a patch on the lower back, 20 minutes after exercise bouts of various lengths and intensities. DPCP is an antigen that triggers the development of a brand new immune response - the strength of the immune response is assessed by applying more DPCP to the skin four weeks later and measuring the resulting redness and skin thickening.

According to Professor Neil Walsh, Director of the Extremes Research Group in the School of Sport, Health & Exercise Sciences and lead author of the paper:

“The good news is that our findings actually sit well with current thinking on endurance training, which also suggests that shorter intense bouts of exercise are important for improving performance. So it’s not at odds with an optimal endurance athlete’s training programme.”

Walsh adds: “We can all learn from this, from top athletes to the recreational athlete. Cast your mind back to some notable examples of top athletes succumbing to illness at a crucial juncture; Paula Radcliffe forced to pull out of the BUPA Great North Run in May 2011 due to a chest infection and a chest infection causing Sir Chris Hoy to withdraw from the European Track Championships in October of the same year. There’s no empirical evidence to suggest that they were suffering immune suppression due to their training, but they’re certainly not alone in experiencing colds and other infections, while performing very heavy training.”

“Optimising immunity is important for athletes as a survey of elite GB performers showed that infections of the upper respiratory tract are a leading cause of under-performance, second only to joint injury. What we now need to find out is the ultimate balance between training and managing our immune response.”

Professor Neil Walsh will be discussing how to avoid getting sick in hard training and competitions at ISENC14, a major international Sports & Exercise Nutrition Conference in Newcastle on 16-18 December.

Publication date: 4 December 2014